For industry standard (non-milspec) fasteners, PTC provides a pretty good one (metric and english) with Pro/E Foundation, but you need to bounce the geometry against the specs because there are errors. Of course, the specs (especially DIN and ISO) can be pricey.
When you find out about mil-spec fastener libraries I'd be obliged if you'd share your findings with me. Did you try a web search? Many mil specs impose industry specs (e.g. ANSI B1.1) to control form and fit. For these you can simply add the mil-spec parts numbers as instances to the family tables.
I didn't really answer your question but I hope this helped some.
What you get with Foundation may vary depending on your sales person and the deal you make with him/her, so you may not have received it with Pro/E at all. I did.
If the library was provided with your Foundation, it is probably buried somewhere on your hard disk. Here's a quick way to find a directory containing a standard part. Using the Find (or Search) utility of Explorer to look for WA.PRT. That is the generic part for the Type A washer per ANSI B18.1.1 (I think that's the spec number). If you find it, then you're on the right track. Be sure to add all desired directories to SEARCH.PRO so that you don't have to hunt and peck every time you need to get to a fastener.
If you did NOT get the fasteners library with Foundation, then there's an off chance you can download from PTC. If not, then you can always buy it from PTC or RAND. Whatever the price, it's a small price to pay rather than modeling all those parts yourself!
I found the library buried on a network drive. Now I have to figure out how to get it into Intralink and apply the company part numbers. A bit of work up front but it will save us having 50 different models of an M3x6 pan head screw.